Air rotary drill bit



Jan. 7, 1969 H, vEsP 3,420,324

AIR ROTARY DRILL BIT Filed April 15. 1966 Lama QM ATTORAZE'X United States Patent Office 3,420,324 Patented Jan. 7, 1969 3 Claims ABSTRACT OF THE DISCLOSURE A shroud with continuous vertically disposed cylindrical surfaces is telescoped over a conventional bit body to adapt it for air drilling by controlling the size of the air passages to reduce them so the air velocity is increased.

This invention pertains to improvements in air rotary drill bits particularly adapted to high speed drilling operations with compressed air for removing the cuttings.

It has been established that a .3000 foot-per-minute air velocity is required to properly clean the hole of cuttings and bring them to the top, this velocity being obtained by the size of the air compressor and the annular area between the drill pipe and the diameter of the hole. Due to the application of standard oil field bits designed for use with drilling mud or water as a circulation agent, large annular areas have been left in the bit castings and, when these bits were converted to be used with air, the basic design was not altered.

The oil field bits, commonly on the market, are moditied by welding cylindrical shrouds having cutouts which fit the shirttails thereby providing a bit having an outline which is sized relative to said bore guage to provide an air velocity past the lower air discharge edge and up past the cylindrical surface suitable for air drilling. a

It is therefore one of the objects of this invention to arrange the rotary bit so that the air to be exhausted is much lower in the cutter area.

Another object is to arrange the rotary bit with a greatly reduced annular area between the bit body and the hole being drilled.

Still another object of this invention is to provide a rotary bit arrangement that causes high velocity air movement which, in turn, cleans the bottom of the drill hole, bringing up coarse cuttings to reduce recirculation of these cuttings and thus reducing regrinding and minimizing wear.

Further features and advantages of this invention will appear from a detailed description of the drawings in which:

FIG. 1 is a side elevation of a standard rotary bit.

FIG. 2 is a perspective view of the air control shroud incorporating the features of this invention.

FIG. 3 shows the rotary bit incorporating the features of this invention operating in the drill hole.

FIG. 4 is a top plan view of the standard rotary bit shown in FIG. 1.

FIG. 5 is a top plan view of the assembly shown in FIG. 3.

As an example of one embodiment of this invention, there is shown a conventional standard air rotary drill bit (FIG. 1) having the usual bit body 11 and tapered threaded shank 12. The usual cones 13 are journaled in the usual downwardly depending shirttail portions 14 between which are formed the cut-away areas 15. The usual air discharge openings 16 are formed in the bit body 11, these openings being supplied with air pressure pumped down through the center of the shank 12 and the drill pipe 17 carrying the bit. In this standard construction of FIGS. 1 and 4, air escapes at the crotch 18 and up through the cut-away areas 15 between the shirttail portions 14 so that low velocity eddy currents develop at the bottom 19 of the hole 20, leaving cuttings from the cones 13 stranded there, resulting in needless recutting and rehashing of these particles with the resulting excessive wear on the rotary bit.

To overcome these difliculties, there has been provided a specially constructed shroud 21 (FIGS. 2 and 3) comprising a cylindrical body 22 having a series of cut-out arched notches 23 terminating in the lower air discharge edge 24 of the cylindrical body 22 so arranged as to he slipped over the bit 10 as shown in FIGS. 3 and 5 and welded or otherwise secured at 25 in an airtight manner about the portions 14 of the body 11 of the bit 10. A suitable cap ring 25a is secured in airtight manner to the upper edge 26 of the cylindrical body 22 and has its bore 27 secured in an airtight manner on the surface 28 of the bit body 11. It will thus be noted that the air blast from the discharge openings 16 must go down and escape past the lower edge 24 of the shroud 21 closely adjacent the bottom 19 of the hole 20 being drilled. It will be further noted in FIG. 5 that the outside surface 29 of the shroud 22 closely presents a continuous annular surface to the hole 20 being drilled so as to effect high velocity upward air flow along thebore of the hole to properly carry up all cuttings dislodged at the bottom 19 of the hole as the air escapes past the edge 24 of the shroud, inasmuch as the diameter of said continuous vertically disposed cylindrical surface of said bit body is only slightly smaller than the bore gauge diameter of said cones.

While the apparatus herein disclosed and described constitutes a preferred form of the invention, it is also to be understood that the apparatus is capable of mechan ical alteration without departing from the spirit of the invention and that such mechanical arrangement and commercial adaptation as fall within the scope of the appendent claims are intended to be included herein.

Having thus fully set forth and described this inven tion, what I claim and desire to be obtained by United States Letters Patent is:

1. An air rotary drill bit comprising, a bit body, shirttails extending downwardly from said body, a tapered threaded shank connected to the upper end of said body, roller cones journaled on said shirttails, air discharge outlets in said body discharging into the area inside of said shirttails and cones, a continuous vertically disposed cylindrical surface attached on the upper portion of said bit body above said shirttails and cones, downwardly extending shroud portions from said cylindrical surface extending between and connected with the side edges of said shirttails terminating in an air discharge edge extending between said shirttails and cones, and a cap ring interconnecting the top of the cylindrical surface and the bit body forming an airtight seal therebetween.

2. An air rotary drill bit as set forth in claim 1 wherein the diameter of said continuous vertically disposed cylindrical surface of said bit body is only slightly smaller than the bore gauge diameter of said cones.

3. An air rotary drill bit as set forth in claim 1 wherein said continuous vertically disposed cylindrical surface of said bit body is sized relative to said bore gauge being cut so as to provide an air velocity of escape past said lower air discharge edge and up between said cylindrical surface and the hole being bored in excess 1,159,087 11/1915 of 3000 feet per minute. 1,231,159 6/1917 1,256,694 2/1918 References Cited 1,582,332 4/1926 UNITED STATES PATENTS 5 1,289,179 12/1918 Hughes 175-340 1,666,711 4/1928 MacDonald 175-334 X 2,261,546 11/1941 Gipson 175-340X NILE Reed 175-339 Hughes 175-339 Hughes 175-339 Brutus 175-339 X Reed 175-339 Schumacher 175-339 Primary Examiner. 

